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BACKGROUND:Muscle weakness is a common symptom after coronavirus disease 2019(COVID-19)infection and affects the ability to perform daily activities in humans during recovery.Low-frequency pulsed magnetic field stimulation at a strength of 1.5 mT and a frequency of 3 300 Hz can enhance the maximal voluntary contraction and strength endurance of human skeletal muscle by inducing and activating classical transient receptor potential channel 1(TRPC1),which produces a series of pathological support effects on muscle tissue.It has not been studied whether this means will improve muscle weakness in patients recovering from COVID-19. OBJECTIVE:To select the low-frequency pulsed magnetic field for magnetic stimulation of lower limb muscle groups in patients with COVID-19,in order to observe the effect of this stimulation on the improvement of muscle weakness of lower limb muscle groups in patients with COVID-19 during the recovery period. METHODS:Fourteen patients infected with COVID-19(Omicron strain)positive for Innovita COVID-19 Ab Test(Colloidal Gold)and accompanied by muscle weakness were recruited and randomly divided into two groups:a test group receiving magnetic field stimulation and a control group receiving sham treatment,respectively.The total duration of the trial was 3 weeks.The test group was given low-frequency pulsed magnetic stimulation of the lower limbs every 48 hours and the control group was given the same intervention procedure as the test group but with sham stimulation.Patients in both groups were not informed whether the magnetic stimulation apparatus was running or not.Nine sessions were performed in both groups and the changes in the maximum voluntary contraction,explosive leg force and strength endurance of the local muscle groups of the lower limbs were subsequently observed in both groups. RESULTS AND CONCLUSION:Among the eight local muscle groups collected,seven local muscle groups in the test group showed an increase in the maximum voluntary contraction value after 3 weeks of low-frequency pulsed magnetic field stimulation.In the control group,there were only three muscle groups with improvement in the maximum voluntary contraction.The rate of improvement in the anterior and posterior muscle groups of the left leg in the test group was significantly higher than that in the control group.The longitudinal jump height and peak angular velocity of the knee joint in both groups were improved compared with the pre-test measurement,and the elevation rate of jumping height in the test group was higher than that in the control group.Under the fatigue condition,the decline rates of peak angular velocity of the knee joint and jumping height in the test group decreased significantly,while those in the control group did not change significantly.The above data confirmed that the low-frequency pulsed magnetic field stimulation with the intensity of 1.5 mT and frequency of 3 300 Hz could improve the muscle strength of more local muscle groups in the lower limbs of patients with COVID-19 during the recovery period compared with the human self-healing process,and the whole-body coordination ability and functional status based on explosive leg force of the legs could be significantly improved.Therefore,low-frequency pulsed magnetic field stimulation can be used as an effective,non-exercise rehabilitation tool to improve muscle weakness in the lower limbs of patients with COVID-19.
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As drug carriers, magnetic nanoparticles can specifically bind to tumors and have the potential for targeted therapy. It is of great significance to explore non-invasive imaging methods that can detect the distribution of magnetic nanoparticles. Based on the mechanism that magnetic nanoparticles can generate ultrasonic waves through the pulsed magnetic field excitation, the sound pressure wave equation containing the concentration information of magnetic nanoparticles was derived. Using the finite element method and the analytical solution, the consistent transient pulsed magnetic field was obtained. A three-dimensional simulation model was constructed for the coupling calculation of electromagnetic field and sound field. The simulation results verified that the sound pressure waveform at the detection point reflected the position of magnetic nanoparticles in biological tissue. Using the sound pressure data detected by the ultrasonic transducer, the B-scan imaging of the magnetic nanoparticles was achieved. The maximum error of the target area position was 1.56%, and the magnetic nanoparticles regions with different concentrations were distinguished by comparing the amplitude of the boundary signals in the image. Studies in this paper indicate that B-scan imaging can quickly and accurately obtain the dimensional and positional information of the target region and is expected to be used for the detection of magnetic nanoparticles in targeted therapy.
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Acústica , Simulação por Computador , Magnetismo , Nanopartículas de Magnetita , TomografiaRESUMO
Objective To investigate the effect of pulsed magnetic radiation on BBB permeability of hippocampus in Sprague-Dawley rats at different exposure intensity.Methods A total of 72 male SD rats were randomly divided into sham exposure group,positive control group and magnetic field treatment groups (100,400,800,1 200 mT,30 pulses each group).At three hours after exposure,the morphological structure of hippocampus was evaluated by HE staining,the extravasation of albumin around microvessels in rat hippocampus was detected immunohistochemically,the EB extravasation around microvessels was observed with Evans blue (EB) fluorescence method,and the levels of BBB-related protein ZO-1 and Occludin in hippocampus were measured with Western blot assay.Results Compared with the control group,no significant change in the hippocampus morphology structure,the extravasation of albumin and EB around the microvessels were observed after the pulsed magnetic exposures.The protein levels of ZO-1 and Occludin had no changes in the exposed groups (P＞ 0.05) except that ZO-1 was significantly reduced in 1 200 mT exposure group (t =14.26,P ＜ 0.05).Conclusions Low-frequency pulsed magnetic field could not affect the permeability of BBB in SD rats but impairs the integrity of BBB at 1 200 mT.
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@#Objective To investigate the effect of different dosage of pulsed magnetic field on expression of platelet-derived growth factor-A (PDGF-A) in rabbits with carotid atherosclerosis after carotid endarterectomy (CEA). Methods Carotid atherosclerosis were modeled in 50 New Zealand rabbits with air-drying lesion combined with high fat feed. All animals were treated with double side carotid endarterectomy after 2 months, and were randomly divided 3 groups: 0.6 T group, 1.0 T group and the blank control. The expression of platelet-derived growth factor-A were detected with immunohistochemistry 1 month, 2 months and 3 months after CEA. Results The expression of PDGF-A in treated groups were lower significantly than that in controls (P<0.05) 2 month after CEA, and it was the lowest in 1.0 T group, lower in 0.6 T group 3 month after CEA. Conclusion The pulsed magnetic field therapy can decrease the expression of PDGF-A, which might be helpful to prevent the carotid from restenosis.
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Objective To examine the neuroprotective effect of pulsed magnetic field in a animal focal cere-bral ischemica-reperfusion injury model. Methods Forty-eight Sprague-Dawley (SD) rats were randomized into 3 groups, a sham-operation group, a model group and a pulsed magnetic field group, with rats 16 in each group. Mid-dle cerebral artery occlusion (MCAO) method was employed to establish the focal cerebral ischemia-reperfusion inju-ry model in rats of model group and pulsed magnetic field group. Rats in sham-operation group was subject to the same operation procedure but not underwent ischemia-reperfusion. The infarction volume, histopathological damage and expressions of IGF-1 in ischemic brain tissue were investigated to evaluate the effect of pulsed magnetic field. Results The infarction volume was reduced, histopathological damage alleviated and expressions of IGF-1 in ische-mic brain tissue elevated in the pulsed magnetic field group as compared against the model group (P<0.05). Con-clusions Pulsed magnetic field might provide neuro-protection against cerebral ischemia-reperfusion injury.
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This paper introduces general guidelines for designing and constructing a magnetic stimulator (MS). These guidelines cover the theoretical concepts, hardware aspects and necessary components. RLC model producing the impulses in MS is focused on and the way to calculate the parameters of the model is presented. Some factors that influence induced magnetic field are discussed. Experiments are carried through with self-developed round coil and 8-shaped, and Tesla meter is used to detect the magnetic fields. The experiments data show that the distribution of the induced magnetic fields by the two coils are tailored to those of theoretical calculation adopted now. A simulation experiment to measure magnetic field in brain has been completed.
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Objective: To investigate the reversal effects of pulsed magnetic fields(PMF) on the drug resistant cell line K562/ADR in vitro and their mechanism.Methods: MTT assay was used to determine the IC50 of ADR on K562/S and K562/ ADR cell lines,the detriment of PMF on the K562/ADR cell line and the reversal effects of the drug resistance after treatment with different frequencies of PMF.Flow cytometry(FCM) was applied to the assessment of concentration of intracellular ADR.Results: The drug-resistance multiple of the K562/ADR cell line was 29.36.PMF did not affect the growth of the K562/ADR cell line.Different frequencies of PMF produced different effects on the IC50 of the K562/ADR cell line.In the same condition,70Hz PMF produced the most significant effect and increasea the concentration of intracellular ADR.Conclusion: PMF can reverse the multidrug resistance of K562/ADR by enhancing the drug concentration in K562/ADR cells,and its frequency is correlated with its reversal effect:low fregucncy produces better effect.